A method and system are described for the continuous remote monitoring of the position and advance speed of a pig device inside a pipeline suitable for transporting a pressurized fluid, wherein the pipeline consists of a plurality of pipe sections joined to each other by welding. The method comprising the following steps: continuous acquisition and registration, by a plurality of measurement stations equipped with vibroacoustic sensors discretely located along the pipeline, of vibroacoustic signals due to hydraulic pressure transients, and/or to the vibrations generated by the pig device in movement in the contact/friction phases on the welding seams, and/or to other physical variations of the pipeline; analysis and processing, by a centralized control unit, of the vibroacoustic signals registered by the measurement stations to reveal, identify and reference the hydraulic/acoustic transients produced by the pig device during contact/friction with the weldings and/or with other variations in the internal section of the pipeline; continuous calculation of the linear position and advance speed of the pig device in relation to the time lapse between the vibroacoustic signals registered by at least two measurement stations installed along the pipeline.
|
1. A method for the continuous remote monitoring of a position and advance speed of a pig device inside a pipeline suitable for transporting a pressurized fluid, wherein the pipeline includes a plurality of pipe sections joined to each other by welding seams, the method comprising the following:
continuously acquiring and recording, by a plurality of measurement stations equipped with vibroacoustic sensors discretely located along the pipeline, of vibroacoustic signals due to the vibrations generated by contact/friction of the pig device with the welding seams of the pipeline and/or with other physical variations locally present in multiple pipe sections of the pipeline;
analyzing and processing, by processing circuitry, the vibroacoustic signals registered by the measurement stations to reveal, identify and reference hydraulic/acoustic transients produced by the pig device as a result of contact/friction with the welding seams and/or with other variations of an internal section of the pipeline; and
continuously determining the linear position and advance speed of the pig device in relation to a time lapse between the vibroacoustic signals registered by at least two measurement stations installed along the pipeline,
wherein the determining of the linear position and advance speed of the pig device is performed by a first measurement station situated on a first side of the pipeline with respect to the position of the moving pig device and a second measurement station situated on the opposite side of the pipeline with respect to the position of said moving pig device, and
wherein the linear position and advance speed of the pig device are determined by analysis of cross-correlation on sliding time windows between the vibroacoustic signals registered by said two measurement stations installed along the pipeline, wherein a time instant of maximum correlation between the vibroacoustic signals is equal to a difference in the arrival times at said two measurement stations of the hydraulic/acoustic transients generated by the pig device and wherein the time is converted to distance by using known information on sound propagation speed in the fluid transported by the pipeline.
12. A system for the continuous remote monitoring of a position and advance speed of a pig device inside a pipeline suitable for transporting a pressurized fluid, wherein the pipeline includes a plurality of pipe sections joined to each other by welding seams, the system comprising:
a plurality of measurement stations equipped with vibroacoustic sensors discretely located along the pipeline, wherein each measurement station registers the vibroacoustic signals due to the vibrations generated by contact/friction of the pig device with the welding seams and/or to other physical variations locally present in the multiple pipe sections of the pipeline; and
processing circuitry operatively connected to said plurality of measurement stations and configured to:
analyze and process the vibroacoustic signals registered by the measurement stations to reveal, identify and reference hydraulic/acoustic transients produced by the pig device as a result of contact/friction with weldings and/or with other variations of internal sections of the pipeline, and
continuously determine a linear position and advance speed of the pig device in relation to a time lapse between the vibroacoustic signals registered by at least two measurement stations installed along the pipeline,
wherein determination of the linear position and advance speed of the pig device is performed by a first measurement station situated on a first side of the pipeline with respect to the position of the moving pig device and a second measurement station situated on the opposite side of the pipeline with respect to the position of said moving pig device, and
wherein the linear position and advance speed of the pig device are determined by analysis of cross-correlation on sliding time windows between the vibroacoustic signals registered by said two measurement stations installed along the pipeline, wherein a time instant of maximum correlation between the vibroacoustic signals is equal to a difference in the arrival times at said two measurement stations of the hydraulic/acoustic transients generated by the pig device and wherein the time is converted to distance by using known information on sound propagation speed in the fluid transported by the pipeline.
15. A method for the continuous remote monitoring of a position and advance speed of a pig device inside a pipeline suitable for transporting a pressurized fluid, wherein the pipeline includes a plurality of pipe sections joined to each other by welding seams, the method comprising the following:
continuously acquiring and recording, by a plurality of measurement stations equipped with vibroacoustic sensors discretely located along the pipeline, of vibroacoustic signals due to the vibrations generated by contact/friction of the pig device with the welding seams of the pipeline and/or with other physical variations locally present in multiple pipe sections of the pipeline;
analyzing and processing, by processing circuitry, the vibroacoustic signals registered by the measurement stations to reveal, identify and reference hydraulic/acoustic transients produced by the pig device as a result of contact/friction with the welding seams and/or with other variations of an internal section of the pipeline;
continuously determining the linear position and advance speed of the pig device in relation to a time lapse between the vibroacoustic signals registered by at least two measurement stations installed along the pipeline; and
acquiring data relating to the linear position of the welding seams between the pipe sections forming the pipeline and data relating to possible variations and/or anomalies on the internal section of the pipeline,
wherein the identification of pressure peaks generated by the pig device while passing through the welding seams between the pipe sections forming the pipeline and the data relating to possible variations and/or anomalies of the internal section of the pipeline are obtained by calculating the Short Term Average over Long Term Average (STA-LTA) of the vibroacoustic signal recorded by a single measurement station and a definition of a threshold value on the resulting signal,
wherein the determining of the linear position and advance speed of the pig device is performed by a first measurement station situated on a first side of the pipeline with respect to the position of the moving pig device and a second measurement station situated on the opposite side of the pipeline with respect to the position of said moving pig device, and
wherein the linear position and advance speed of the pig device are determined by analysis of cross-correlation on sliding time windows between the vibroacoustic signals registered by said two measurement stations installed along the pipeline, wherein a time instant of maximum correlation between the vibroacoustic signals is equal to a difference in the arrival times at said two measurement stations of the hydraulic/acoustic transients generated by the pig device and wherein the time is converted to distance by using known information on sound propagation speed in the fluid transported by the pipeline.
2. The method according to
3. The method according to
acquiring data relating to the linear position of the welding seams between the pipe sections forming the pipeline and data relating to possible variations and/or anomalies on the internal section of the pipeline.
4. The method according to
5. The method according to
wherein x(n) is the n-th sample of the vibroacoustic signal registered by a single measurement station and sampled at the time instant nT, with T equal to the sampling period, and n, m, k are parameters consisting of integers which define the duration of the time window and m<k.
6. The method according to
wherein x2(n) and x3(n) are the n-th sample of the vibroacoustic signals registered by two measurement stations positioned on opposite sides of the pig device, sampled at the time instant nT, with T equal to the sampling period, and n, m, k are integers which define the duration of the time window.
7. The method according to
8. The method according to
obtaining sound propagation parameters, including speed and attenuation, in various pipe sections of the pipeline by processing composite signals; and
evaluating a correlation of the vibroacoustic measurements between adjacent measurement stations, wherein the signal to be processed includes both the acoustic noise generated by the pig device moving along the pipeline and pressure variations in the fluid.
9. The method according to
continuously analyzing a statistical type of waveforms relating to passages of the pig device through the welding seams between the pipe sections forming the pipeline and possible variations and/or anomalies of the internal section of said pipeline, and different sound attenuation due to various propagation distances, wherein a sound propagation model, which includes calculation of the sound speed and attenuation in the fluid, is continuously acquired and experimentally updated.
10. The method according to
identifying anomalies of the welding seams and/or the pig device based on the analyzing and determining.
11. The method according to
identifying anomalies of the welding seams and the pig device based on the analyzing and determining.
13. The system according to
14. The system according to
|
The present invention relates to a method and system for the continuous remote monitoring, in passive mode, of inspection or pigging operations of pipelines used for transporting pressurized fluids, in particular for detecting, in real time, the position and advance speed of a pig device inside the pipeline, any possible damage and/or malfunctioning of the pig device, any possible anomaly of the internal section of the pipeline and any possible blockage positions of the pig device.
The method and system according to the invention envisage the installation of equipment suitable for the purpose along the pipeline, equipped with vibroacoustic sensors (hydrophones in contact with the fluid and/or accelerometers/geophones in contact with the wall of the pipe), the transmission of data and processing of the signals on the part of a control unit. The continuous monitoring method and system can be applied to pipelines for the transportation of pressurized fluids, generally long-distance oil-pipelines and gas-pipeline of international strategic importance.
Technologies currently known for monitoring during pigging operations of pipelines used for the transportation of pressurized fluids envisage the identification of the sound waves generated by the friction between the disks of the pig device and the welding seams of the pipeline, or they require the installation of suitable active transmitters of the acoustic and/or electromagnetic type on the pig device. Other detection techniques of the position, in the event of a blockage in the pig device, envisage the generation of hydraulic transients on one side of the pipeline and the measurement of the propagation times in the free section of the same pipeline.
The document WO 2010/010318 describes a method based on the detection of the noise generated by the pig device in movement during its passage in the proximity of a series of vibroacoustic sensors located along the pipeline and positioned at a short distance from the pipe. This document, however, does not describe analysis techniques in real time of the signals, neither is the noise generated by the pig device passively exploited for identifying malfunctionings of the same and/or physical anomalies of the pipeline.
The documents GB 2305989, U.S. Pat. No. 4,541,278 and GB 2394549 describe systems which use the vibrations produced by the pig device for tracking it inside the pipeline. These systems, however, perform the physical analysis of the pipeline (corrosion, flaws, etc.) with “ad hoc” instrumentation installed onboard the pig device. The position of the pig device is reconstructed a posteriori by processing the data collected during the pigging operations.
The document U.S. Pat. No. 5,417,112 proposes the installation of a pair of sensors (geophones and/or magnetometers) at a known distance along a pipeline for identifying the passage of the pig device and its movement speed during the passage in the proximity of the same sensors. This document also describes the possibility of measuring the time between the signals produced by the pig device in the passage through consecutive weldings, positioned at a known distance, for measuring the movement speed of the pig device itself. In U.S. Pat. No. 5,417,112, however, processing techniques that envisage a cross-correlation between the two geophones for accurate localization in intermediate positions, are not used.
The document U.S. Pat. No. 4,590,799 proposes tracking a pig device with the use of two geophones in contact with the pipeline at a known distance, and the activation of trigger signals in correspondence with the passage of the pig device in the proximity of said geophones.
The document U.S. Pat. No. 2,820,959 envisages the use of an active source of electromagnetic waves assembled on the pig device and an external detection apparatus of these waves for localizing said pig device.
The document EP 0122704 proposes localizing the pig device by identifying its passage through two section variations, predefined and geolocated a priori along the route of the pipeline.
The document US 2011/0139538 describes the use of a series of acoustic sensors distributed along the pipeline, using optical fibre, for determining the position of the pig device at each moment. The method is effective and accurate in the localization but requires the presence of a continuous series of sensors along the route of the pipeline.
The document US 2011/0282591 envisages the installation of RFID (acronym of “Radio Frequency IDentification”) sensors along the pipeline.
The document U.S. Pat. No. 5,549,000 proposes an analysis of the noise generated by the pig device during its movement for determining the conditions of the same pig device and/or of the pipeline. The system envisages the installation of accelerometers on the walls of the pipe for measuring, at the moment of passage of the pig device, the vibrations generated by the pig device itself and which interact with the pipe/fluid system. The estimation of the conditions of the system is localized around the sensor (in the order of tens of meters).
The document US 2011/0301882 describes the use of accelerometers/hydrophones for the registration and continuous analysis of the passive noise (ultrasounds having a frequency in the order of 1 MHz) generated by the flow and/or by the pig device in movement for obtaining the percentage of solids (sands) contained in the fluid being transported.
Finally, the document WO 2009/067769 envisages the positioning of hydrophonic sensors along the pipeline and the insertion, in the body of the pig device, of an apparatus capable of generating a pressure transient, such as, for example, the fast opening of a by-pass valve, between the two sides of the pig device. The pressure transient is revealed by the hydrophones positioned at the two sides of the pig device and, by processing the arrival times of the waves at the hydrophones, the position of said pig device is obtained.
Numerous patent documents according to the known art generally envisage the detection (acoustic and/or electromagnetic) of the pig device at the moment of its passage in correspondence with sensors suitably located along the pipeline and therefore the interpolation of the position of said pig device in intermediate positions using those already detected. The measurement precision can consequently only be increased by reducing the distance between the sensors and/or increasing their number. Similar techniques are sued for the localization of acoustic sources not in movement, for example in the localization of a leakage point in a pipeline as described in the document U.S. Pat. No. 4,289,019.
An objective of the present invention is therefore to provide a method and system for the continuous remote monitoring of inspection or pigging operations of pipelines used for transporting pressurized fluids which is capable of solving the drawbacks of the known art mentioned above, in an extremely simple, economical and particularly functional manner.
More specifically, an objective of the present invention is to implement techniques for localizing acoustic sources not in movement, by suitably calibrating the time cross-correlation parameters, in order to extend them to a source in movement. The distance between the sensors is therefore only influenced by the necessity of being capable of registering the signals emitted by the pig device. The nature of the signals is low-frequency (less than 100 Hz) and the sensors can also be positioned at a distance of various tens of kilometers for pipelines having a diameter greater than 8″-10″.
The method according to the invention continuously reconstructs the position and the speed of the pig device by processing the vibroacoustic signals emitted from the pig device itself, using cross-correlation techniques of sliding time windows. The signals are registered by at least two sensors positioned at opposite sides with respect to the position of the pig device. The method according to the invention also proposes strengthening the estimation of the possible anomalies of the pig device and/or pipeline also using the count of acoustic events generated by the passage of said pig device through the weldings of the pipe, which are positioned at known distances.
As far as the detection of anomalies of the pig device and/or pipeline are concerned, the methods and systems according to the known art generally effect an analysis of the vibroacoustic signals generated by the pig device and/or flow of fluid and registered by appropriate sensors (typically accelerometers). In this way, the medium/high frequencies of the signal emitted are processed, in the order of kHz if generated by the pig device and in the order of MHz if generated by the flow of fluid passing inside the pipeline. The area of pipeline being examined is limited to around each sensor, or, in other words, at a distance of less than 10 meters from each sensor.
The method according to the present invention, without excluding the possibilities offered by the methods according to the known art, proposes, on the other hand, an analysis of the repeatability of the waveforms generated by the pig device in the friction phase of the welding seams in order to identify anomalies of the welding and/or of the pig device itself, also at a distance of several kilometers. As the vibroacoustic signal undergoes an attenuation during its propagation inside the pipeline, the method according to the invention proposes equalizing the signals registered, before comparing them, by compensating of the propagation effects according to the proper physic-mathematical models, whose parameters are calibrated with experimental measurements that re-exploit the vibroacoustic signals inside the pipe (see, in this respect, international patent application PCT/EP2013/077116 in the name of the same applicant).
Further objectives of the method and system according to the present invention are:
These objectives according to the present invention are achieved by providing a method and system for the continuous remote monitoring of inspection or pigging operations of pipelines used for the transportation of pressurized fluids as specified in the independent claims.
Further characteristics of the invention are indicated by the dependent claims, which are an integral part of the present description.
In general, the method and system according to the invention combine the continuous remote tracking techniques of the pig device during the inspection, with the detection techniques of anomalies of the same pig device, and also the pipeline under examination. Time domain cross-correlation procedures of the vibroacoustic signals are used for obtaining an accurate localization of the pig device also at distances reaching tens of kilometers from the sensors installed along the pipeline.
The method and system according to the invention therefore envisage:
The characteristics and advantages of a method and system for the continuous remote monitoring of inspection or pigging operations of pipelines used for transporting pressurized fluids according to the present invention will appear more evident from the following illustrative and non-limiting description, referring to the enclosed schematic drawings, in which:
With reference to
The method according to the invention envisages the continuous remote registration of the vibroacoustic signals and noise generated by the pig device 10 during contact/friction with the weldings and/or with other variations in the internal section of the pressurized pipeline 12. The vibroacoustic signals are also analyzed to identify and localize possible anomalies in the pig device 10 that have arisen during the inspection of the pipeline 12.
The system according to the invention comprises the installation of a plurality of measurement stations 14 equipped with vibroacoustic sensors (hydrophones, accelerometers, geophones, etc.) and located discretely along the pipeline 12, also at a distance of tens of kilometers between pairs of adjacent measurement stations 14. Each measurement station 14 registers the vibroacoustic signals due to the hydraulic pressure transients, and/or the vibrations generated by the pig device 10 in movement in the contact/friction phases on the welding seams, and/or with other physical variations (ovalizations, deformations, deposits and corrosion) present locally in the numerous pipe sections of the pipeline 12.
The vibroacoustic signals emitted inside the pipeline 12 and registered by the various measurement stations 14 are synchronized temporally with an absolute time reference system 16, such as, for example, a global satellite navigation system (GNSS or GPS), and are then sent to a centralized control unit 18 for multichannel processing (
The detection distance of the vibroacoustic signals depends on the attenuation of said vibroacoustic signals which propagate inside the pipeline 12, the dynamic sensitivity of the hydrophonic measurement sensors and the bandwidth of the measurement instrumentation (frequency range: 0.1-10 Hz). With the use of vibroacoustic measurement equipment suitable for the purpose, in pipelines 12 for the transportation of gas/oil having an average diameter of about 20″, the detection distance of the pig device 10 can reach about 30 km from the measurement point. With an increase in the diameter of the pipeline 12 and pressure of the fluid, the remote detection distance of the pig device 10 increases to up to about 50 km from the measurement point.
For implementing and verifying the method and system according to the invention, some vibroacoustic measurement campaigns were performed on off-shore and on-shore pipelines in service for the transportation of natural gas (
The method according to the invention envisages two distinct localization procedures of the pig device 10 inside the pipeline 12, which can be independently and/or jointly implemented.
The first procedure (count of the sound peaks) requires having data available relating to the linear position of the welding seams along the pipeline 12, which derives from the length of each single section of pipe (typically equal to 12 meters) which composes the pipeline 12 itself, in addition to data relating to possible variations and/or anomalies of the internal section of the pipeline 12. In particular, the vibroacoustic signals registered by at least one measurement station 14 positioned at a suitable distance from the pig device 10 for receiving the signals generated by the movement of the pig device 10 itself, are acquired and processed. The data available allow the detection and the localization of the hydraulic/acoustic transients produced by the pig device 10 during its passage through the above section variations, to be revealed, identified and referenced (
Defining x(n) the nth sample of the vibroacoustic signal registered by the single measurement station 14 and sampled at the time instant nT (with T equal to the sampling period and n an integer), the signal STA-LTA is obtained as:
wherein n, m, k are integers which define the duration of the time window and m<k. In the exemplificative diagram of
The second procedure (cross-correlation on sliding time windows) does not require a knowledge of the linear position of the welding seams along the pipeline 12. The linear position of the pig device 10 during the inspection of the pipeline 12 is calculated continuously by the analysis of the cross-correlation on sliding time windows between the vibroacoustic signals generated by the same pig device 10 and registered by at least two measurement stations 14 installed along the pipeline 12, of which a first measurement station 14 is situated on a first side of the pipeline 12 with respect to the position of the pig device 10 in movement and the second measurement station is situated on the opposite side of the pipeline 12 with respect to the position of said pig device 10 in movement (
With reference to the scheme of
with m an integer which defines the duration of the time window.
In the exemplificative diagram of
For both procedures, if the pig device 10 interrupts its advancement, there are no longer vibroacoustic signals produced by the passage through the section anomalies (welding seams) and the procedures described provide the position of the last detection, whereas the advance speed of the same pig device 10 becomes null.
The method according to the invention also comprises obtaining the sound propagation parameters (speed and attenuation) in the various sections of pipe of the pipeline 12 through the processing of composite signals, evaluating, for example, the correlation of the vibroacoustic measurements between adjacent measurement stations 14. The signal to be processed consists, in this case, of both the acoustic noise generated by the pig device 10 during the inspection route in the pipeline 12, and by pressure variations in the fluid connected to the variability of the pressure regime of the pumps/compressors (see international patent application PCT/EP2013/077116 in the name of the same applicant).
A further specific feature of the method according to the invention is to perform a continuous analysis of the statistical type, of the waveforms (for example amplitude, energy, bandwidth and frequency centroid) produced during the passages of the pig device 10 through the welding seams between the sections of pipe forming the pipeline 12 and the possible variations and/or anomalies of the internal section of said pipeline 12, also considering the different sound attenuation due to the different propagation distances (
The statistical analysis of the waveforms emitted within certain acceptability thresholds, for example by the training and use of neural networks, allows anomalous events to be identified and localized along the pipeline 12, due to malfunctioning of the pig device 10 and/or variations in the section inside the pipeline 12 itself.
It can thus be seen that the method and system for the continuous remote monitoring of inspection or pigging operations of pipelines used for transporting pressurized fluids according to the present invention achieve the objectives previously indicated.
The method and system for the continuous remote monitoring of inspection or pigging operations of pipelines used for transporting pressurized fluids according to the present invention thus conceived can in any case undergo numerous modifications and variants, all included in the same inventive concept. The protection scope of the invention is therefore defined by the enclosed claims.
Giunta, Giuseppe, Bernasconi, Giancarlo, Del Giudice, Silvio
Patent | Priority | Assignee | Title |
10359307, | Mar 30 2015 | NIPPON SEIKI CO , LTD | Liquid surface position detection device |
10539480, | Oct 27 2017 | Mueller International, LLC | Frequency sub-band leak detection |
11519807, | Dec 13 2019 | Halliburton Energy Services, Inc | Method and system to determine variations in a fluidic channel |
Patent | Priority | Assignee | Title |
4590799, | Mar 23 1983 | PIPELINE INTEGRITY INTERNATIONAL LIMITED | Pipeline pig tracking |
5417112, | Jan 11 1993 | TDW Delaware, Inc. | Apparatus for indicating the passage of a pig moving within an underground pipeline |
5460046, | May 19 1994 | TDW Delaware, Inc | Method and apparatus for ultrasonic pipeline inspection |
5549000, | Jun 27 1994 | Texaco, Inc. | Passive acoustic detection of pipeline pigs |
6082193, | Apr 11 1997 | PURE TECHNOLOGIES LTD | Pipeline monitoring array |
8620602, | Nov 30 2007 | ASEL-TECH TECHNOLOGIA E AUTOMACAO LTDA | System for detecting leaks in single phase and multiphase fluid transport pipelines |
20030161428, | |||
20030192693, | |||
20040089358, | |||
20100135447, | |||
20110103189, | |||
20110139538, | |||
20110149688, | |||
20110162454, | |||
20110313671, | |||
20120106676, | |||
20120137781, | |||
20120210793, | |||
20120243376, | |||
20130096393, | |||
20130223565, | |||
20140009598, | |||
20140025319, | |||
20140165731, | |||
20150300907, | |||
20150323119, | |||
20160341583, | |||
CA2728818, | |||
GB2462096, | |||
WO2009067769, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
May 11 2015 | BERNASCONI, GIANCARLO | ENI S P A | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 036142 | /0751 | |
May 14 2015 | ENI S.p.A. | (assignment on the face of the patent) | / | |||
May 26 2015 | GIUNTA, GIUSEPPE | ENI S P A | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 036142 | /0751 | |
May 26 2015 | GIUDICE, SILVIO DEL | ENI S P A | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 036142 | /0751 | |
Nov 21 2023 | ENI S P A | ENIVIBES S R L | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 066150 | /0405 |
Date | Maintenance Fee Events |
May 20 2022 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
Date | Maintenance Schedule |
Nov 20 2021 | 4 years fee payment window open |
May 20 2022 | 6 months grace period start (w surcharge) |
Nov 20 2022 | patent expiry (for year 4) |
Nov 20 2024 | 2 years to revive unintentionally abandoned end. (for year 4) |
Nov 20 2025 | 8 years fee payment window open |
May 20 2026 | 6 months grace period start (w surcharge) |
Nov 20 2026 | patent expiry (for year 8) |
Nov 20 2028 | 2 years to revive unintentionally abandoned end. (for year 8) |
Nov 20 2029 | 12 years fee payment window open |
May 20 2030 | 6 months grace period start (w surcharge) |
Nov 20 2030 | patent expiry (for year 12) |
Nov 20 2032 | 2 years to revive unintentionally abandoned end. (for year 12) |